Summer 2014 Internship Projects John Venables Alaska Center for Energy and Power 1

Case Study of Solar Power in the Northwest Arctic Borough Lessons Learned Paper from Organic Rankine Cycle Machine Used by Cordova Electric Cooperative.

Solar Power in NAB

11 Rural Communities ~7,500 Residents 39,000 square miles – Second largest borough in Alaska Small plane access year round Seasonal boat access until rivers freeze No road system – Some ATV/Snowmobile Access during winter Deering, Alaska

Kotzebue is the central hub of the region with an airport that can support jets. Ships must harbor offshore since the waters aren’t deep enough. Average cost of gasoline ~$8.5/gal Average cost of diesel for power generation ~$4/gal Average Pre-PCE cost of Electricity is $0.63/kWh Pilot Solar Array in Ambler

Water and Sewer Treatment Plants add big costs to communities Solar arrays designed to offset the base power load of these facilities with average rated capacity - 10 kW Grant Funded by Coastal Impact Assistance Program Cost ~$75,000 $7.5 per watt First array was installed March 2013, 8.4 kW array in Ambler

Year Solar Production in Ambler

Annual Production from Ambler: ~6.981 MWh Fuel savings: ~500 gallons = $2,105 Electric $0.62 / kWh: $4,330 Pounds of CO 2 offset: 28,406.3 = 3 acres of trees Lifetime Electric Savings (25 year lifespan) = ~$108,205 ~13 year payback Excess power sold back to utility (~$0.14/kW)

Currently 6 communities have these arrays 5 new arrays being installed Summer/Fall 2014 Circular Array in Kobuk Multiple Angle Array in Noatak

Organic Rankine Cycle Machine Lessons Learned from failed ORC project in Cordova First cold climate use of ORC coupled with diesel generator Goal was to take waste heat from the generator to produce extra electrical power Rankine Cycle is basis for steam engines used today ORC uses an organic working fluid with phase change at much lower temperatures than water

ORC Cycle Diagram

Pratt & Whitney Power Systems, Inc PureCycle Model 280 coupled to Electro-Motive Division 3.7 MW diesel generator Uses R245fa, pentafluoropropane, as the working fluid Also used as foam-blowing agent in insulation industry No flash point, also no chlorine so won’t deplete ozone P&W ORC Model 280 EMD 3.7 MW Generator

Hot liquid resource from the generator between 195F-300F (90C-149C) Cooling < 85F (30C) Greater temperature difference, more power generated For full output power, flow rate of hot resource between gallons per minute Gross output of 280 kW, net output of 260 kW (parasitic load from working fluid pump) Shutdown if power less than 80 kW

Hasn’t been operated since May 5 th, 2013 More power used than being produced by the ORC Cooling issues: cooling tower freezing/tearing, thermostats on the generator shutting, not able to get temperature difference far enough apart Well designed, but issues dealing with the manufacturer, expensive shipping of parts to Alaska Good concept but technology isn’t at a point to be sustainable Cooling Tower Used by CEC

Thank You ACEP! Special Acknowledgments: Mentor: Daisy Huang Northwest Arctic Borough: Ingemar Mathiasson Robert Bensin Cordova Electric Cooperative: Danny Ackmann